Various arrangements for mounting implements such as back hoes to prime movers are known in the art. For example the arrangements shown in U.S. Pat. Nos. 4,403,429 Harringer, 3,313,431 Kelly, 4,049,139 Stedman, and 3,027,026 Couquet and Australian Patent No. 243,547 Couquet. Such arrangements have been employed in order to improve the flexibility and scope of operation of the implement and have met with varying degrees of success. U.S. Pat. No. 4,403,429 Haringer, discloses an articulated arm for supporting a bucket, mounted on a rotating turret of an excavator and designed for digging parallel to either side of a prime mover. Limits to rotary movement of arms of the articulated arm comprise mechanical stops fixed to the arms. Hence limits to movement and orientation of the bucket is not variable with movement of the arms. Instead, the mobile flexibility of operation through the linkage is mechanically limited even when the implement is in no danger of contacting the prime mover.
U.S. Pat. No. 3,313,431 Kelly discloses a similar double arm linkage arrangement for a back hoe wherein the articulated arm is mounted on a side shift attachment on a prime mover with pivotal movement of the arms about the pivots provided by rack and pinion actuators. The provision of a side shift attachment enables a lateral change in limits at the linkage mounting to the prime mover, however limits to orientated movement of the back hoe relative to the prime mover is fixed, so that there is a similar limitation to flexing and orientation mobility of operation.
U.S. Pat. No. 4,049,139 Stedman discloses a linkage arrangement for a back hoe comprising two linkage arms pivotally connected together, the linkage arrangement being pivotally connected to the prime mover. Pivotal movement between the two arms is provided by a hydraulic swing motors mounted therebetween. The combined hydraulic swing motors give a high degree of flexing mobility such that the linkages can be folded to enable an implement to be stowed close to the prime mover for transport and perform increased manipulative tasks. However, due to this high degree of flexing mobility, skilled operator control of swing motor rotation is required depending on a current position and orientation of the linkage relative to the prime mover to ensure that the implement does not strike the prime mover under normal operating conditions. Operability of the linkage arrangement thus leads to a compromise of operational safety for manipulation.
U.S. Pat. No. 3,027,026 Couquet and Australian Patent No. 243,547 Couquet, disclose a linkage for an excavator such as a trencher having a single arm pivotally mounted on a support frame, and pivotally supporting a digger attachment on a distal end thereof. Pivotal movement of the arm relative to the support frame, and of the digger attachment relative to the arm is by means of manually operated gear actuators whereby the linkage can be set up for a particular operation. An additional actuator is also provided for pivotal movement of the arm relative to the support once the linkage has been set up. Operating flexibility and mobility is similar to Stedman apart from the slow manually actuated controls reducing risk of contacting the support frame. Otherwise, like Steadman, it suffers compromise.
Due to the various compromise situations of the above art which utilise hierarchically controlled actuation and limiting, where each link in a flexible chain of links is both actuated and limited from the orientation of the preceding link, the total of pivot freedom angles equal the orientation change of the last link, and tool, from the support structure. In some cases the hierarchically controlled actuation and limiting is provided from the link before the preceding link by way of parallelogram through the preceding link. In these cases the orientation of the link does not change. Compromise between total freedom values necessary to increase manipulation, and self contact with the machinery is apparent.
Other apparatus such as the linkage arrangement described in U.S. Pat. Nos. 5,201,235 by Sutton and 4,609,322 by Quant disclose single structural link's between the prime mover and the bucket tool. Bucket actuation in the form of hydraulic rams are interconnected between the prime mover, the link and the bucket tool. The interconnection between the prime mover, lift arm and bucket is not a closed assembly as the ram actuation severely effects the geometry and moment values and therefor changes the relative response to the bucket orientation through rotary movement of the lift arm. In the case of such apparatus, this is generally a consequence of providing a linkage arrangement to drive rotation of the implement which, as described for this form of art, seeks to keep the implement's actuated position at a pre-set level to that of the ground during actuated rotation of the main arm. The inter connection of the ram based tool actuation and relative orientation of the tool is suitable for some applications utilising a single link but not for maximising flexibility through freedom angle totals within mechanical limits and without self contact. The bucket actuation being inter linked in such way creates a moment variation of force and top dead centre difficulties as a combined inherent rotation and an actuated rotation concentrate through a single actuating link about a high pivotal value. In both above mentioned forms of art, and many similar, level or orientation only of a tool is anticipated, not mobility in the sense of manipulation requiring flexibility. Had they envisaged such use they would have had a closed assembly by adding the closing orientation base, and actuated from it. They have not purposely established an independent orientation base, at or as, the distal end of the linkage arm. In the prior art devices mentioned either a compromise is made to the freedom of the implement to avoid contact with the prime mover or to safety by increasing the degrees of freedom values. The prior art does not increase the ability to move and vary orientations of an implement about a support structure without striking the support structure with the implement, and arrangement hence are unsuitable to do so.
Other prior art includes such apparatus used in the raising of work platforms such as cherry pickers, some fire engine lifts, etc. These items utilise a closed parallelogram assembly for links between the platform and the vehicle such that each link separately rotates from an orientation base and presents the same orientation at a distal end base as a first end base of each linkage arm assembly and all bases of rotation remain unchanged in its orientation with respect to the structure. All joint bases serve jointly as a distal end base for one arm assembly and as a first end base for another thereby integrating all arm assemblies with a constant orientation relative to the support structure. As each preceding link is rotated with respect to its pivotal connection, the supporting base for the next link is counter-rotated one degree for each degree of rotation of that link, successively. Although such apparatus is highly manipulative and very useful in operation within one half hemisphere off the vehicle, it does not provide a safe working environment for operation about three sides of the structure or vehicle. Such apparatus, when utilised to approach one side of an opposing pair of sides of a vehicle, can be traversed into the vehicle in an attempt to get to the opposite side of the vehicle. By limiting the counter-rotation, the work platform tool or implement can be made to withdraw around the structure as this traverse takes place.
All the above art have, for one reason or another, embraced the hierarchical nature of chain linked movements and compromised with increased link end to link end actuated and limited rotational total values and the resultant possibility of the tool striking the prime mover when working to either side thereof and therefore susceptible to operator error. Alternatively, they have totally countered the orientation side of the heirarchical nature to find a different compromise. Hence with the above prior art devices, there is a limit to the acceptable increase in rotational limits. This limitation on rotational values and limits to avoid striking the prime mover poses an unnecessary restriction on the rotational movement of the tool when positioned for alternate work applications away from the prime mover where there is no danger of striking the prime mover, or access to opposing sides reducing mobility of operation of the device for work operations and for stowing for transportation.
The present invention is thus addressed to methods and apparatus for supporting an implement such that the implement is movable relative to a support member which is also movable relative to a structure, movement of the implement and support member being limited by mechanical and/or mechanically operated limits, such methods and apparatus enabling the integration of multiple links as an integrated chain of links between a support structure and a tool implement or object to increase the ability to move and vary orientation of the implement within a limit envelope, or at least provide the public with a useful choice.
For example in the case of a back hoe, such methods and apparatus may provide a linkage arrangement for the support and positioning of an implement, which enables an increase in the possible scope of operation of the implement mounted thereon compared to conventional support linkages, while still ensuring that the implement does not contact the prime mover when supported close to the prime mover, and which enables the implement to be supported within weight distribution, and dimension requirements for road transportation.
Further aspects and advantages of the present invention will become apparent from the ensuring description which is given by way of example only.